Bird droppings and tree sap are tough on urban benches because they can stain, etch, and turn into sticky messes. The best approach is to focus on three things: location, protection, and cleaning.
First, look at where the bench sits. If it is directly under a tree, you are making the problem worse. Move it a few feet away if possible. If the bench is fixed, trim any overhanging branches or install an overhead cover such as a small pergola, canopy, or even a wide patio umbrella. Simply breaking the fall line from branches to the bench will stop most sap and droppings before they land.
Second, protect the surface. For a wooden bench, lightly sand and clean it, then apply at least two coats of outdoor spar varnish, marine-grade polyurethane, or a penetrating wood sealer. For metal frames, a coat of automotive wax or ceramic spray makes sap and droppings much easier to wipe off. For plastic or composite benches, use a UV-protectant spray. After the main finish cures, add a layer of paste wax as a sacrificial coat. It gives the bench a little shine and keeps stains from bonding tightly to the surface.
Third, if the bench is not used all day, use a fitted waterproof cover or a simple tarp secured with bungee cords. It is not the most stylish solution, but it works. Remove the cover during peak sitting hours and put it back at night or during bad weather.
Cleaning is where most people go wrong. Bird droppings are acidic, so remove them quickly with warm water, mild dish soap, and a soft sponge or brush. Avoid harsh scraping. For tree sap, do not scrub hard. Soften the sap with isopropyl alcohol, hand sanitizer, or a small amount of vegetable oil. Let it sit for a minute, wipe gently, then wash the area with soapy water to remove any residue.
If birds keep targeting the area around the bench, avoid feeding them nearby. You can also add reflective tape, a fake owl, or bird spikes on nearby ledges and signs, but not on the bench itself. That helps redirect birds without making the bench uncomfortable.
Finally, make a simple routine: wipe the bench down once a week, remove droppings and sap as soon as you notice them, and refresh the wax or sealant every season. That prevents permanent staining and keeps the bench looking clean with far less effort.